Turfgrass Root Basics

P turfgrasses are characterized by an extremely fine, fibrous root system. This leads to considerable frustration on the part of researchers due to the time-consuming, costly procedures required to accurately study and measure turfgrass roots. Nevertheless, the monitoring of rooting depth and functional viability on a regular basis is an important dimension in any turf manager's information assemblage for key decision-making activities. Roots are a hidden, but major component of a turfgrass plant. Roots function in water absorption, nutrient uptake, anchorage, and sod strength. Actually, the unique, extensive, fibrous root system of turfgrass has a extraordinary ability to take up nutrient elements, and thereby protects the quality of groundwater. Turfgrass shoots/leaves have their meristematic region and allied cell division and elongation activities located at the base. Thus, the leaf tip is the oldest portion of the leaf and the leaf base the youngest. As a result the oldest part of the leaf is cut off during mowing. Just the opposite exists for roots, where the tip of the root most distant from the originating turfgrass crown or stem node region is the youngest part of the root. Thus, in harvesting sod the meristems or growing tips of the roots are cut off. Consequently, new root initiation must originate from the meristematic tissues in the crowns and the nodes on lateral stems, such as stolons and rhizomes. This basic principal dictates that the shallower the soil depth cut during sod harvesting, the more rapid the rate of sod transplant rooting, assuming there is no water stress. The principle sites through which water and nutrients are taken up from the soil solution into the roots and translocated upward to the shoots are via the root hairs. These are very delicate, whitish, outward extensions of individual epidermal or surface root cells. These root hairs are microscopic and thus cannot be seen by the naked eye. However, the surface area of these roots is 5 to 10 times greater than the primary and secondary root system that is visible to the eye. Therefore, understanding how environmental factors, cultural practices, and chemicals affect root hairs is a major concern in relation to maximizing the ability of turfgrasses to take up vital water and nutrients. Most turfgrasses are perennials, but certain perennial species have root systems that behave as an annual. Included among the annual-type root systems are such coolseason turfgrasses as perennial ryegrass (Lolium perenne), bentgrass (Agrostis spp.), and rough bluegrass (Poa trivialis). The critical period in the loss of root systems of cool-season turfgrasses is during mid-summer when soil temperatures at a 4-inch (100 mm) depth exceed 80°F (17°C) (Figure 1). Warm-season turfgrasses may be characterized as having annual root systems on occasions when spring root decline (SRD) occurs. The critical time in terms of a limited root system for warm-season turfgrasses is in the spring when soil temperatures at a 4-inch (100-mm) depth reach 64°F (18°C) (Figure 2). The genetic rooting ability of various turfgrass species and cultivars in terms of depth and mass varies considerably (Table 1). They range from very deep-rooted species, such as the bermudagrasses (Cynodon spp.), with a depth of 7 to 8 feet (2.1-2.4 m) under mowed conditions, to the shallow root systems of the zoysiagrasses (Zoysia spp.), American buffalograss (Buchloe dactyloides), and